A known direct smelting process for a metalliferous material, which relies principally on a molten bath as a smelting medium, and is generally referred to as the HIsmelt process, is described in International application PCT/AU96/00197 (WO 96/31627) in the name of the applicant.
The HIsmelt process as described in the International application in the context of direct smelting a metalliferous material in the form of iron oxides and producing molten iron includes the steps of:
(a) forming a bath of molten iron and slag in a vessel;
(b) injecting into the bath: (i) metalliferous material, typically iron oxides; and (ii) solid carbonaceous material, typically coal, which acts as a reductant of the iron oxides and a source of energy; and
(c) smelting metalliferous material to iron in the molten bath.
The term “smelting” is herein understood to mean thermal processing wherein chemical reactions that reduce metal oxides take place to produce molten metal.
The HIsmelt process also includes post-combusting reaction gases, such as CO and H2 released from the bath, in the space above the bath with oxygen-containing gas, typically air, and transferring the heat generated by the post-combustion to the bath to contribute to the thermal energy required to smelt the metalliferous materials.
The HIsmelt process also includes forming a transition zone above the nominal quiescent surface of the bath in which there is a favourable mass of ascending and thereafter descending droplets or splashes or streams of molten metal and/or slag which provide an effective medium to transfer to the bath the thermal energy generated by post-combusting reaction gases above the bath.
In the HIsmelt process metalliferous material and solid carbonaceous material are injected into a molten bath through a number of solids injection lances (sometimes referred to as “tuyeres”) which are inclined to the vertical so as to extend downwardly and inwardly through a side wall of a direct smelting vessel and into a lower region of the vessel so as to deliver at least part of the solids material into a molten metal layer in the bottom of the vessel. To promote the post-combustion of reaction gases in an upper part of the vessel, a blast of hot air, which may be oxygen-enriched, is injected into an upper region of the vessel through a downwardly extending hot air injection lance. Off gases resulting from post-combustion of reaction gases in the vessel are taken away from the upper region of the vessel through an off gas duct. The vessel includes refractory-lined water cooled panels in the side wall and the roof of the vessel, and water is circulated continuously through the panels in a continuous circuit.
The HIsmelt process enables large quantities of molten iron to be produced by direct smelting of metalliferous material. To enable such levels of production, large quantities of both metalliferous material and carbonaceous material must be supplied to the vessel.
The above description is not to be taken as an admission of the common general knowledge in Australia or elsewhere.